Modelling biological N fixation and grass-legume dynamics with process-based biogeochemical models of varying complexity

This work was conducted by the Models4Pastures consortium project under the auspices of FACCE-JPI. Funding was provided by: the New Zealand Government to support the objectives of the Livestock Research Group of the Global Research Alliance on Agricultural Greenhouse Gases; AgResearch’s Strategic Science Investment Fund as a contribution to the Forages for Reduced Nitrate Leaching (FRNL) research programme; the input of UK partners was funded by DEFRA and also contributes to the RCUK-funded projects: N-Circle (BB/N013484/1), UGRASS (NE/M016900/1) and GREENHOUSE (NE/K002589/1). R.M. Rees and C.F.E. Topp also received funding from the Scottish Government Strategic Research Programme. Lutz Merbold and Kathrin Fuchs acknowledge funding received for the Swiss contribution to Models4Pastures (FACCE-JPI project, SNSF funded contract: 40FA40_154245/1) and for the Doc.Mobility fellowship (SNSF funded project: P1EZP2_172121). Lorenzo Brilli, Camilla Dibari and Marco Bindi acknowledge funding received from the Italian Ministry of Agricultural Food and Forestry Policies (MiPAAF).Peer reviewedPublisher PD

In vivo imaging of pancreatic tumours and liver metastases using 7 Tesla MRI in a murine orthotopic pancreatic cancer model and a liver metastases model

<p>Abstract</p> <p>Background</p> <p>Pancreatic cancer is the fourth leading cause of tumour death in the western world. However, appropriate tumour models are scarce. Here we present a syngeneic murine pancreatic cancer model using 7 Tesla MRI and evaluate its clinical relevance and applicability.</p> <p>Methods</p> <p>6606PDA murine pancreatic cancer cells were orthotopically injected into the pancreatic head. Liver metastases were induced through splenic injection. Animals were analyzed by MRI three and five weeks following injection. Tumours were detected using T2-weighted high resolution sequences. Tumour volumes were determined by callipers and MRI. Liver metastases were analyzed using gadolinium-EOB-DTPA and T1-weighted 3D-Flash sequences. Tumour blood flow was measured using low molecular gadobutrol and high molecular gadolinium-DTPA.</p> <p>Results</p> <p>MRI handling and applicability was similar to human systems, resolution as low as 0.1 mm. After 5 weeks tumour volumes differed significantly (p < 0.01) when comparing calliper measurments (n = 5, mean 1065 mm³+/-243 mm³) with MRI (mean 918 mm³+/-193 mm³) with MRI being more precise. Histology (n = 5) confirmed MRI tumour measurements (mean size MRI 38.5 mm²+/-22.8 mm²versus 32.6 mm²+/-22.6 mm²(histology), p < 0,0004) with differences due to fixation and processing of specimens. After splenic injection all mice developed liver metastases with a mean of 8 metastases and a mean volume of 173.8 mm³+/-56.7 mm³after 5 weeks. Lymphnodes were also easily identified. Tumour accumulation of gadobutrol was significantly (p < 0.05) higher than gadolinium-DTPA. All imaging experiments could be done repeatedly to comply with the 3R-principle thus reducing the number of experimental animals.</p> <p>Conclusions</p> <p>This model permits monitoring of tumour growth and metastasis formation in longitudinal non-invasive high-resolution MR studies including using contrast agents comparable to human pancreatic cancer. This multidisciplinary environment enables radiologists, surgeons and physicians to further improve translational research and therapies of pancreatic cancer.</p

Complex dynamics and elementary economic theory

Contrary to the view that complex dynamical systems are curiosities at a safe distance from core tenets of economics, it is shown that they undermine a few fundamental constructs and models. The long run macroeconomic equilibrium defined as the limit of a sequence of short run equilibria is shown to be a problematic construct in simple aggregate models. The demonstration also undermines the very notion of the long run as used in mainstream economics, and the dictum that prices are flexible in the long run

The role of scavenging in the spread of bovine tuberculosis in free-living ferret populations in New Zealand

Ferrets (Mustela furo) exhibit high prevalences of bovine tuberculosis (Tb) in some areas of New Zealand. Whether the disease will persist in ferret populations in the absence of external sources of Tb infection is unknown and subject to extensive debate. The pathology of the disease in free-living ferrets suggests that in this species infection arises primarily through ingestion of tuberculous carrion. This thesis investigated the scavenging behaviour of ferrets with a view to determining their importance as a wildlife reservoir for the spread of bovine tuberculosis in New Zealand. A field trial was undertaken on farmland in North Canterbury, New Zealand, to assess the relative contribution that scavenging of brushtail possum, ferret and hedgehog carcasses is likely to make to the observed tuberculosis prevalence in ferrets. A total of 108 carcasses were laid out in the field for 4-week periods in various seasons. Ferrets visited 35 percent of all the carcasses, with 16 percent of these visits resulting in scavenging. Ferrets were more than twice as likely to visit ferret carcasses as carcasses of other species (p0.05). The number of visits by ferrets declined in winter, but the scavenging rate per visit did not vary seasonally. In a second trial, an outdoor enclosure and time-lapse video equipment were used to investigate the feeding behaviour of 10 adult wild-caught ferrets in response to ferret, hedgehog and possum carcasses. Ferrets fed more on possum carcasses than on the other carcass types, whereas there was no significant difference in the number of feeding events on hedgehog and ferret carcasses. On at least 15 of 22 occasions, ferrets ate parts of carcasses that would have put them at high risk of exposure to Mycobacterium bovis, had the carcass been infected with Tb. Even when they were not actively feeding, ferrets often had considerable physical contact with ferret carcasses. Few differences in feeding behaviour were observed between sexes, although male ferrets tended to eat more of a carcass than did females. Ferrets fed more frequently during winter but these feeds tended to be shorter in duration. The implications of the observed scavenging behaviour for Tb transmission are discussed. Scavenging rates in North Canterbury were markedly lower than those observed by other researchers in Otago. It seems unlikely that scavenging alone is capable of maintaining Tb within North Canterbury ferret populations, although in other areas that have higher ferret densities and scavenging rates this remains a possibility